Coated paper was conventionally used as paper for industrial products, labels on the containers of frozen foods, and indoor and outdoor advertising posters. However, coated paper has poor waterproof properties, and therefore, waterproof resin films comprising polyolefin synthetic paper has more recently been used.
These resin films are well known, and have been disclosed in, JP-B-46-40794 (the term “JP-B” as used herein means an “examined Japanese patent publication”), JP-B-49-1782, JP-A-56-118437 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-57-12642 and JP-A-57-56224.
However, such polyolefin synthetic paper shrinks when heated at 100° C. or higher. Accordingly, during printing with a heat-fixing type electrophotographic printer or a heat-fixing type electrophotographic copier that fixes toner by heat energy, such as plain electrophotographic copier (PPC) or laser beam printer (LBP), excessive curling occurs on the printed face side due to the dimensional change of the resin film during heat fixing. This results in poor paper delivery during the continuous printing of multiple sheets. Therefore, the use of polyolefin synthetic paper has met with limited success. Further, when using a direct heat-sensitive printer in which the temperature of a heat-sensitive head is from 100 to 180° C., the heat curls the paper towards the printed side of the heat-sensitive recording. As a result, paper delivery is poor, and this interferes with the continuous printing of multiple sheets.
For preventing paper curling, laminated recording paper comprising heat resistant pulp paper and polyolefin synthetic paper has also been disclosed (JP-A-62-198497). However, for such a lamination process, a processing manufacturer must purchase raw material from both a film manufacturer and a paper manufacturer. This leads to higher costs for the manufacture of recording paper. Therefore, a low curl recording paper provided from a less expensive process is desirable.
Further, adhesive labels for the prevention of altering, or adhesive labels impossible of re-covering are demanded and these labels have been put to practical use. However, re-covering-preventing adhesive labels are expensive, and there still remain problems of the residual adhesive on the peeled surface and of dust adhesion.
Attempts to solve this problem have been disclosed in JP-A-8-99377 and JP-A-10-258476, but they have drawbacks such as inferior waterproof properties, and special processing techniques, (e.g., notching,) are required to provide easy peeling.
The present invention solves the problems with prior techniques. For example, an object of the present invention is to provide recording paper and label paper with excellent waterproof properties and with less curling by heat while using the recording paper in a heat-fixing type electrophotographic printer, a heat-fixing type electrophotographic copier or a direct heat-sensitive printer, while still providing excellent paper delivery, and the ability to provide continuous printing of multiple sheets.
A further object of the invention is to provide recording paper and label paper with excellent waterproof properties as the base materials of masking seals and re-covering-preventing labels, and requiring no special process to start peeling.
The present invention involves preparing recording paper comprising a resin film (A) containing a thermoplastic resin, and at least one of an inorganic fine powder and an organic filler, and having the heat of crystallization of 60 J/cm3 or lower. The height of curl of the recording paper is reduced after printing while utilizing a heat-fixing type electrophotographic printer, a heat-fixing type electrophotographic copier or a direct heat-sensitive printer. In addition, good printability is realized in the continuous printing of multiple sheets. Further, the recording paper is suitable as recording paper requiring no special process to start peeling by further comprising a layer (C) capable of layer-from-layer peeling having a peeling strength of from 5 to 150 g/cm width, and a surface layer (D) having a breaking strength of 500 g/cm width or less on resin film (A).
The recording paper according to the present invention is characterized in that printing is performed with a heat-fixing type electrophotographic printer, a heat-fixing type electrophotographic copier or a direct heat-sensitive printer, and that the heights of the curls of four corners of A-4 size (210 mm×297 mm) paper after two minutes or more from printing with a heat-fixing type electrophotographic printer, a heat-fixing type electrophotographic copier or a direct heat-sensitive printer are 50 mm or less on average.
In a preferred embodiment of the invention, resin film (A) contains from 35 to 97 wt % of a thermoplastic resin and from 65 to 3 wt % of at least one of an inorganic fine powder and an organic filler, the thermoplastic resin is preferably a crystalline resin, an amorphous resin or an elastomer, or a mixture of two or more thereof, and the thermoplastic resin is more preferably a mixture of a crystalline resin and an amorphous resin, or a mixture of a crystalline resin and an elastomer.
The crystalline resin is an olefin resin, more preferably a propylene resin. The amorphous resin is preferably selected from terpene resins, carboxylic acid vinyl ester resins, acrylic esters, methacrylic esters and petroleum resins, and the elastomer is preferably selected from thermoplastic styrene elastomers, thermoplastic olefin elastomers, thermoplastic urethane elastomers and thermoplastic ester elastomers.
Resin film (A) is preferably at least uniaxially stretched. The porosity of resin film (A) is preferably 75% or less. Resin film (A) preferably has a multilayer structure.
Resin film (A) is preferably subjected to oxidation treatment or provided with image-receiving layer (B). Further, resin film (A) preferably has layer (C) capable of layer-from-layer peeling having a peeling strength of from 5 to 150 g/cm width, and more preferably a surface layer (D), having a breaking strength of 500 g/cm width or less, is laminated on the surface of layer (C) capable of layer-from-layer peeling.
Layer (C) capable of layer-from-layer peeling can be prepared by a coating process. Electrostatic capacity is preferably 5 pF/cm2 or more.
Resin film (A) can be used as label paper laminated with strippable paper (F) through adhesive layer (E).
Further, the present invention includes recording substances using the recording paper and the label paper, and also includes methods of recording with a heat-fixing type electrophotographic printer, a heat-fixing type electrophotographic copier or a direct heat-sensitive printer.